VFD overvoltage on decel trip

[GerryMem]

I'm working on a commercial washing machine which used a Allen Bradley 160 series vfd(discontinued) on a 3 hp 3 phase motor. I've replaced the AB with a Hitatchi WJ-200 vfd and am experiencing an intermittent trip code of overvoltage from deceleration(after its done spinning the clothes at full rpm). This is a high inertia application as the drum and clothes are essentially a flywheel. Will INCREASING the decel TIME setting help to stop overvoltaging the DC bus? I transferred the parameter that was used on the old AB unit of 35 seconds to the new vfd and now I get this issue. What about DC braking? Or should I just let it free run stop?

Thanks

 

[SceneryDriver]

I'm working on a commercial washing machine which used a Allen Bradley 160 series vfd(discontinued) on a 3 hp 3 phase motor. I've replaced the AB with a Hitatchi WJ-200 vfd and am experiencing an intermittent trip code of overvoltage from deceleration(after its done spinning the clothes at full rpm). This is a high inertia application as the drum and clothes are essentially a flywheel. Will INCREASING the decel TIME setting help to stop overvoltaging the DC bus? I transferred the parameter that was used on the old AB unit of 35 seconds to the new vfd and now I get this issue. What about DC braking? Or should I just let it free run stop?

You can set the VFD to freewheel to a stop, or add a properly sized brake resistor. There are cases where you want the drive to be able to control and stop the load quickly, but this doesn't sound like one of those cases. Cheapest to program the drive to allow a freewheel stop. DC braking can be used, but it heats up the motor windings (especially with high inertia loads) and becomes exponentially less effective the slower the motor rotates.

SceneryDriver

 

[SSDriver]

Usually increasing the ramp down/decel time will help with this issue. The other thing is make sure you have the proper torque curve and characteristics set up in the drive for your application. Setting the stop command to coast may work as long as it doesn't create other issues

 

[GerryMem]

You can set the VFD to freewheel to a stop, or add a properly sized brake resistor. There are cases where you want the drive to be able to control and stop the load quickly, but this doesn't sound like one of those cases. Cheapest to program the drive to allow a freewheel stop. DC braking can be used, but it heats up the motor windings (especially with high inertia loads) and becomes exponentially less effective the slower the motor rotates.

SceneryDriver

Thanks. I will try the FRS option first. The bus voltage was hitting the 400 v threshold on decal and tripping. Hopefully they'll fix it. Next I guess will be increase the decal time up from 35 secs. There is a need for DC braking for safety if the door would open to stop it ASAP. I have an input switch to STOP on loss of continuity.

 

[SceneryDriver]

Thanks. I will try the FRS option first. The bus voltage was hitting the 400 v threshold on decal and tripping. Hopefully they'll fix it. Next I guess will be increase the decal time up from 35 secs. There is a need for DC braking for safety if the door would open to stop it ASAP. I have an input switch to STOP on loss of continuity.

Sounds like you need a brake resistor if you need a CAT1 (actively decelerated) E-stop on door open. If the drive trips on overvoltage and you don't have a mechanical brake, you need a way to dissipate the kinetic energy of a load. The resistor does that. Note that it's usually poor from to rely on mechanical brake(s) for STOPPING. They'll wear out quickly, especially with high inertia loads. Holding is fine, stopping is not so such.


SceneryDriver

 

[Jraef]

Understand that DC injection braking is usually limited to a fraction of the VFD's rating (varies by mfr and model). It's tricky to figure out just how much, so just keep in mind that its ability to stop the load is limited to what the components inside of the VFD can handle.

 

[GerryMem]

Understand that DC injection braking is usually limited to a fraction of the VFD's rating (varies by mfr and model). It's tricky to figure out just how much, so just keep in mind that its ability to stop the load is limited to what the components inside of the VFD can handle.

Ok, set to FRS. Taking a LITTLE too long to stop after spin, not much though. Bus voltage was normal (320v) on decel though(good). Question: can I use DC braking while still setting to FRS or do I have to return to (decel to stop) to use the DC braking? Then there is the issue of DC Hold voltage, time and freq. parameters.
Thanks for all the help!!

 

[kwired]

When you make the drive decelerate the motor, you are collecting the energy of the inertia of the load and dissipating that usually as heat in the drive or combination of the drive and a braking resistor. If you don't get rid of that energy fast enough you get high DC bus volts and possible tripping of the drive protection. Slower deceleration time does allow for lesser braking resistor or ability of drive to dissipate the energy.

You probably know this but just throwing it out there. Your new drive must not be equipped to handle such deceleration, at least as is. If option to add braking resistor and you don't have one yet, it may be fine if you add one. If you do already have braking resistor and it still has overvolt trips, the drive may be undersized for braking at the rate it is being asked to do.

 

[GerryMem]

Well: all was well until I checked for faults tonite: got 2 UNDERVOLTAGE faults(but only on 1 of the 2 machines) (which is what the OLD inverters were tripping for). It tripped during constant speed and DC Bus voltage dropped to 175v ,amp output was normal both times and within a minute of one another. I'm starting to think it's the line input voltage is dipping, as this new inverter is now getting an undervoltage fault as well......ugh. Power company is going to put a monitor on my incoming line voltage to see what is going on. I think their line voltage is fluctuating.

 

[kwired]

Well: all was well until I checked for faults tonite: got 2 UNDERVOLTAGE faults(but only on 1 of the 2 machines) (which is what the OLD inverters were tripping for). It tripped during constant speed and DC Bus voltage dropped to 175v ,amp output was normal both times and within a minute of one another. I'm starting to think it's the line input voltage is dipping, as this new inverter is now getting an undervoltage fault as well......ugh. Power company is going to put a monitor on my incoming line voltage to see what is going on. I think their line voltage is fluctuating.

Could be lost/intermittent/partially lost phase within your facility as well. Drive is likely capable of running with only single phase input, as long as output load isn't too high to drain the DC bus voltage too far.

 

[GerryMem]

Could be lost/intermittent/partially lost phase within your facility as well. Drive is likely capable of running with only single phase input, as long as output load isn't too high to drain the DC bus voltage too far.

Forgot to mention: the input voltage is SINGLE phase 220v......

 

[synchro]

Well: all was well until I checked for faults tonite: got 2 UNDERVOLTAGE faults(but only on 1 of the 2 machines) (which is what the OLD inverters were tripping for). It tripped during constant speed and DC Bus voltage dropped to 175v ,amp output was normal both times and within a minute of one another. I'm starting to think it's the line input voltage is dipping, as this new inverter is now getting an undervoltage fault as well......ugh. Power company is going to put a monitor on my incoming line voltage to see what is going on. I think their line voltage is fluctuating.

To have an undervoltage fault with a high inertia load while running at a constant speed , a sag or momentary loss of the AC input voltage would need to persist for several seconds or more. That's because the stored mechanical energy would be keeping the bus voltage up for a while. But with a low inertia load you might get an undervoltage fault with a loss of the AC input over just a few cycles.

 

[kwired]

Drive(s), including the old ones marginally sized for the application?